1. Field of the Invention
The present invention relates to an image scanner and a control method thereof. Particularly, the present invention relates to an image scanner which includes a power saving function, and which is capable of quickly performing necessary processes when the image scanner is returned to a normal mode from a power saving mode, as well as a method of controlling the image scanner.
2. Description of the Related Art
Recently, power saving in image scanners has been promoted, as in the disclosure in Japanese Unexamined Patent Publication No. 2007-060211. Therefore, commonly used are image scanners having a power saving mode in which less power is consumed than in a normal operation mode. FIG. 1 is a block diagram showing a part of a configuration of such an image scanner having the power saving mode.
As shown in FIG. 1, the image scanner includes: an original size sensor circuit 240 configured to detect the size of an original placed for scanning on an unillustrated platen; and a cover open sensor 260 configured to detect whether an unillustrated platen cover is opened or closed. The cover open sensor 260 detects that a user is in the process of closing the platen cover which has been opened to place the original on the platen. Then, at this detection timing, the original size sensor circuit 240 detects the size of an original placed on the platen, and informs a CPU 220 of the size of the original. Such size detection is employed because the original size sensor circuit 240 cannot detect the size of the original in a state where the platen cover is fully closed. Specifically, the original size sensor circuit 240 perceives the size of the original by detecting light which reflects from the original. Once the platen cover is fully closed, the original size sensor circuit 240 detects light reflecting from not only the original but also the platen cover, and accordingly cannot detect the size of the original.
In the image scanner shown in FIG. 1, the CPU 220 acquires the size of the original recognized by the original size sensor circuit 240 through a field programmable gate array (FPGA) 230. In this respect, the FPGA 230 is an integrated circuit capable of configuring a logic circuit by loading circuit information.
For the purpose of enhancing the power saving effect in such a configuration, a scheme of stopping power supply to the FPGA 230 and the original size sensor circuit 240 when the image scanner enters the power saving mode is under consideration. On the other hand, the normal power supply to the cover open sensor 260 continues even in the power saving mode, because the cover open sensor 260 needs to detect that the platen cover is opened.
Once the power supply to the FPGA 230 is stopped, the logic circuit quickly volatilizes (disappears) in the FPGA 230. With this taken into consideration, once the cover open sensor 260 detects that the platen cover is opened in power saving mode, first of all, it is necessary to configure a process circuit 231 in the FPGA 230 by loading circuit information to the FPGA 230. For this reason, only after the process circuit 231 is configured in the FPGA 230, the CPU 220 can communicate with the original size sensor circuit 240, and thus can activate the original size sensor circuit 240.
As described above, the CPU 220 acquires the size of the original while the platen cover is in the process of being closed after the platen cover is once opened. For this reason, if a user closes the platen cover before the CPU 220 activates the original size sensor circuit 240, the CPU 220 fails to acquire the size of the original. As a result, the user is forced to open and then close the platen cover again after the CPU 220 activates the original size sensor circuit 240. This deteriorates the usability of the image scanner.
If power supply to the original size sensor circuit 240 and the FPGA 230 continues in the power saving mode to avoid the problem of the usability deterioration, the continued power supply decreases the power saving effect.